1. Field of the Invention
The present invention is related to a looper thread take-up apparatus externally added to outer end of lower driving shaft of a sewing machine.
2. Description of the Prior Art
The housing of a conventional sewing machine includes a machine bed, a machine column erecting on right end of the machine bed and a machine arm integrally connected with the top end of the machine column and suspending and leftward extending. A lower driving shaft is mounted in the machine bed and an upper driving shaft is disposed in the machine arm. The lower driving shaft via a toothed belt drives the upper driving shaft, whereby the two driving shafts rotate in accordance with a set timing. A needle bar is fitted through the end of the machine arm. The needle is mounted at bottom end of the needle bar and driven by the upper driving shaft to up and down sew a sewing material. A needle plate is disposed on the machine bed in the needle stroke position. A lower knotting hook is mounted in the machine bed near the needle stroke position. The lower knotting hook is driven by the lower driving shaft and cooperates with the needle to knot the thread and complete the sewing operation.
In order to achieve beautiful seam, in each stitching operation, the looper thread must be properly loosened. Conventionally, a thread take-up cam is mounted on the lower driving shaft. Thread guide plates are respectively mounted on two sides of the thread take-up cam. The looper thread is passed through one thread guide plate and then wound over the rim of the thread take-up cam and then passed through the other thread guide plate and finally passed through the eyelet of the lower knotting hook. The thread take-up cam is driven by the lower driving shaft and cooperatively rotates by one circle in each needle stroke travel. The thread take-up cam serves to pull and take up (that is, loosen) the looper thread. Accordingly, the seam on the sewing material will not crimp.
It is necessary to adjust the length of each thread take-up travel in accordance with the thickness and variety of the sewing material so as to adjust the tension of the looper thread to an optimal extent. Therefore, a convenient adjustment of the looper thread take-up apparatus is required. In addition, the thread take-up cam rotates at high speed so that the looper thread is subject to breakage and tangling in the groove of the thread take-up cam. Under such circumstance, it is necessary to detach the thread take-up cam for clearing up the tangling thread. Then, the thread take-up cam is again mounted on the lower driving shaft. In addition to the thread take-up cam, many other components are mounted on the lower driving shaft. Therefore, it is a professional task to detach the thread take-up cam from the lower driving shaft of the sewing machine. Moreover, after clearing up the tangling thread, it is necessary to again laboriously install the thread take-up cam back to its home position. Furthermore, after installed back to the home position, it is necessary to again adjust the timings of the respective components. It often takes one or more than one day to complete these procedures. Such complicated works can be hardly independently done by a clothes manufacturer and specialists of the original manufacturer of the sewing machine are required to complete the works.
It is therefore a primary object of the present invention to provide a looper thread take-up apparatus externally added to outer end of lower driving shaft of a sewing machine. The looper thread take-up apparatus is externally added to the outer end of the lower driving shaft of the sewing machine instead of the thread take-up cam and thread guide structure originally fixedly mounted on the lower driving shaft in the housing of the sewing machine. Accordingly, the looper thread is passed through the looper thread take-up apparatus externally added to the outer end of the lower driving shaft of the sewing machine instead of the thread take-up cam and thread guide structure. In case the looper thread breaks and tangles with the thread take-up cam, it is easy and convenient to clear up the tangling thread from outer side of the sewing machine.
It is a further object of the present invention to provide the above looper thread take-up apparatus in which the looper thread is passed through the looper thread take-up apparatus externally added to the outer end of the lower driving shaft of the sewing machine instead of the thread take-up cam and thread guide structure originally fixedly mounted on the lower driving shaft in the housing of the sewing machine. Therefore, the laborious and troublesome task of detachment of the thread take-up cam can be avoided.
According to the above objects, the looper thread take-up apparatus externally added to outer end of lower driving shaft of a sewing machine of the present invention includes a thread guide structure and a thread take-up cam. The thread guide structure includes a thread guide plate formed with a slot, and two thread guide eyelets respectively disposed on two sides of the slot. The looper thread take-up structure further includes a looper thread tension adjustment structure disposed beside the thread guide structure. The looper thread is first passed through the looper thread tension adjustment structure to adjust the tension and then sequentially passed through the two thread guide eyelets of the thread guide structure and finally guided to the lower knotting hook of the sewing machine. The thread guide structure and the looper thread tension adjustment structure are mounted on outer side of the housing of the sewing machine and are adjacent to the outer end of the lower driving shaft of the sewing machine. The thread take-up cam is detachably disposed at outer end of the lower driving shaft of the sewing machine and rotatable along with the lower driving shaft. The thread take-up cam is directly detachable from the outer end of the lower driving shaft, whereby the lower driving shaft directly drives the thread take-up cam to rotate so as to take up the looper thread passing through the two thread guide eyelets of the thread guide structure.
The looper thread take-up apparatus externally added to outer end of lower driving shaft of a sewing machine further includes a thread guide tube disposed on outer face of machine column of the housing of the sewing machine, whereby the looper thread passing out of one of the thread guide eyelets of the thread guide structure is passed through the thread guide tube and guided to the lower knotting hook of the sewing machine.
In the above looper thread take-up apparatus externally added to outer end of lower driving shaft of a sewing machine, the thread take-up cam is fixed at outer end of the lower driving shaft via a coupling structure. The coupling structure includes: a clamping member fitted at outer end of the lower driving shaft, the thread take-up cam being fixed at one end of the clamping member, the other end of the clamping member being formed with a split and fitted at the outer end of the lower driving shaft, an end of the split being formed with two slopes; a tightening wedge wedged between the slopes of the split of the clamping member; and a bolt passed through the clamping member from one end to the other end thereof, the bolt being screwed into the tightening wedge, by means of tightening the bolt, the tightening wedge pressing the slopes of the split, whereby the other end of the clamping member is radially expanded to abut against the wall of a shaft hole of a pulley fixed at outer end of the lower driving shaft and tightened in the shaft hole.
Alternatively, the looper thread take-up apparatus externally added to outer end of lower driving shaft of a sewing machine of the present invention includes a thread guide structure, a looper thread tension adjustment structure and a thread take-up cam. The thread guide structure includes a thread guide plate formed with a slot, and two thread guide eyelets respectively disposed on two sides of the slot. The thread guide structure being disposed on outer side of the housing of the sewing machine and adjacent to outer end of the lower driving shaft of the sewing machine. The looper thread tension adjustment structure is disposed beside the thread guide structure. The looper thread is first passed through the looper thread tension adjustment structure to adjust the tension and then sequentially passed through the two thread guide eyelets of the thread guide structure and finally guided to the lower knotting hook of the sewing machine. The thread take-up cam passes through the slot of the thread guide structure and is detachably disposed at outer end of the lower driving shaft of the sewing machine and rotatable along with the lower driving shaft. The thread take-up cam is directly detachable from the outer end of the lower driving shaft so as to take up the looper thread passing through the two thread guide eyelets of the thread guide structure.
The above looper thread take-up apparatus externally added to outer end of lower driving shaft of a sewing machine further includes a thread guide tube disposed on outer face of machine column of the housing of the sewing machine. The looper thread passing out of one of the thread guide eyelets of the thread guide structure is passed through the thread guide tube and guided to the lower knotting hook of the sewing machine.
In the above looper thread take-up apparatus externally added to outer end of lower driving shaft of a sewing machine, the thread take-up cam is fixed at outer end of the lower driving shaft via a coupling structure. The coupling structure includes: a clamping member fitted at outer end of the lower driving shaft, the thread take-up cam being fixed at one end of the clamping member, the other end of the clamping member being formed with a split and fitted at the outer end of the lower driving shaft, an end of the split being formed with two slopes; a tightening wedge wedged between the slopes of the split of the clamping member; and a bolt passed through the clamping member from one end to the other end thereof, the bolt being screwed into the tightening wedge, by means of tightening the bolt, the tightening wedge pressing the slopes of the split, whereby the other end of the clamping member is radially expanded to abut against the wall of a shaft hole of a pulley fixed at outer end of the lower driving shaft and tightened in the shaft hole.
The present invention can be best understood through the following description and accompanying drawings wherein: